We are investigating the capacity of the retina to carry out the biosynthesis of its mannose-containing glycoproteins, with special emphasis being placed on the biosynthesis of the saccharide moieties of the glycoprotein, rhodopsin. We are studying the biosynthesis and properties of polyisoprene-mannose-containing lipids by the retina, and are investigating their role in the biosynthesis of glycoproteins, as well as the participation of vitamin A and its analogues in these processes. These studies are being carried out primarily with preparations from the retina of the embryonic chick, and with rat and bovine retinas.